The present invention concerns levels for measuring the horizontality of flat surfaces.
Measuring the horizontality of flat surfaces is important in many engineering tasks. Most conventional levels are based on the motion of an air bubble in water in a sealed transparent tube, placed on a ruler with a flat base. These levels vary in dimension, price and accuracy. While these known levels are popular on account of their low price and the fact that they consist of a single convenient and robust unit, they have the disadvantage of having a relatively low degree of sensitivity and a low dynamic range.
Livnat and Kafri, Rev. Sci. Inst. 53, 1779 (1982) have suggested a level based on moire deflectometry (see also Kafri, Optics Letters 5, 555 (1980), and Phys. Bull. 33, 197 (1982) which is of high accuracy down to 10.sup.-5 rad, has a high dynamic range and may provide absolute measurement of any inclination angle. However, this level requires a collimated light beam and thus it is not suitable for use in construction and other heavy duty jobs where collimated light sources are not available.